Paper machine broke control

ABSTRACT

There is described a paper making system that includes (1) a broke tank, couchpit or other receptacle for broke stock fibers and (11) a machine chest or other container that feeds a supply of suitably prepared fibers to the paper machine. The invention is the improvement that comprises means of restricting the flow of suitably prepared fibers from the machine chest, and in their place feeding broke stock fibers from the broke tank, couchpit or other receptacle for broke stock fibers so that, when the paper making system is malfunctioning, the paper machine can be kept running on substantially broke stock. The system has the advantage of being able to avoid the excessive production of broke.

United States Patent 1151 3,660,226 McKeown 1 1 May 2, 1972 1541 PAPER MACHINE BROKE CONTROL 1,670,874 5/l928 Bankus et al. ..162/264 [72] inventor: Lewis A. McKeown, 473 Mayfair Avenue,

Ottawa, 3 Ontario. Canada i g f g l g D- 88 [22) Filed: June 10, 1970 v 21 Appl. 196.; 44,936

[5 7] ABSTRACT,

There is described a paper making system that includes l a broke tank, couchpit or other receptacle for broke stock Foreign Appliclfio" fibers and l l) a machine chest or other container that feeds a June 1 1 1969 Canada .054 067 Supply suitably Prepared fibers Paper machine The invention is the improvement that comprises means of restrict- 52 11.5. c1 ..162 264 162 191 ,suliably R fibers mm the machme E 1m cl i [1/66 chest, and 1n the1r place feedmg broke stock fibers from the l 58] Fieid H91 264 broke tank, couchpit or other receptacle for broke stock fibers so that, when the paper making system is malfunctioning, the paper machine can be kept running on substantially {56] References Cited broke stock. The system has the advantage of being able to n- STATES PATENTS avoid the excessive production of broke. 1 ,868,291 7/1932 OConnor ..l62/l9l X 8 Claims, 1 Drawing Figure 6/ 54 GROUND I l woo I I6 STOCK BROKE CHEST l 25 PROPORTIONING I METER BOX I STUFF BOX I 2/ I l was 1 1 53 MIXED STOCK 26 27 4 Box CHEST FLOW I 44 22 62 29 1 1 l MACHINE BROKE c112 ST STORAGE L f 24 TANK J 36 34 28 l FOURDRINIER HEAD /46 l DRYERS SECTION BOX DRY END 42 36 32 33 BEVATER 4/ i 3/ 3o FOR DRY BROKE FILTER 2 I COUCH PIT FOR WIRE FAN BROKE STOCK CHEST WET BROKE PIT t PUMP PAPER MACHINE BROKE CONTROL BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to a paper making system having an improved broke system.

In the present disclosure and claims the expression paper making system" means that group of machines and container tanks or receptacles that are used to produce a sheet of paper starting from pulp stock. A typical paper making system includes in combination a pulp stock supply container, blending and proportioning machines, a paper machine, for example a Fourdrinier machine, upon which the sheet of paper is formed, dryers, a broke handling system, container tanks for various waters given up by the crude sheet of paper and pumps to circulate the various fluids involved at various stages in a system for making paper.

2. Description of the Prior Art Broke is the waste produced at any stage in a paper making system. Paper making systems generally include broke systems which enable broke produced during paper making or formed from the completed paper to be returned to the process. Broke may be formed during the process when the paper machine is not running properly. Broke is also formed from the completed paper by trimming and cutting.

The production of a certain amount of broke is inevitable in a paper making system and the mixed stock used to make paper normally contains about to percent of broke. As this is the normal amount of broke produced on a paper machine all the broke is reused in the paper making system, possibly after reconditioning. However, the excessive production of broke has a'number of disadvantages. These disadvantages are:

a. The machine running properties of broke are different from those of mixed stock;

b. It is necessary to store broke. This is particularly a problem with the high speed paper making systems used at present. If such a system breaks down broke can be produced at the rate of 25 tons per hour. The storage of such quantities presents considerable problems.

c. It is not economical to throw away large quantities of broke but a paper machine runs poorly when it is fed too much broke. It may run so poorly that all it will produce is more broke. Further the quality of the product madewhen a system is running poorly is inferior to that made when a system is operating properly.

The present invention avoids the above disadvantages by providing a paper making system that has a novel broke handling system. The paper making system according to the present invention also produces less broke than existing systems.

SUMMARY OF THE INVENTION The present invention relates to a paper making system that includes (i) a broke tank, couchpit or other receptacle for broke stock fibers and, possibly a broke filter stock chest and (ii) a machine chest or other container that feeds a supply of suitably prepared fibers to the paper machine, said machine chest, possibly having associated with it fresh stock supply chests and stock proportioning means and is the improvement that comprises means of restricting the flow of suitably prepared fibers from the machine chest and, in their place feeding broke stock fibers from the broke tank so that, when the paper making system is malfunctioning the paper machine can be kept running on substantially broke stock.

When the sheet breaks on paper machines in existing papermaking systems'the'normal-stock furnish continues to be fed to the machineto keep it operating until the sheet break is repaired. The normal stock fed to the machine is diverted to the broke handling system. 'In the paper :making system according to thepresent invention the normal fumish'of stock to the paper machine is stopped when there is a break and the new furnish usedis largely broke stock.

DESCRIPTION or DRAWINGS An embodiment of a paper making system improved according to the present invention is illustrated diagrammatically in the accompanying drawing.

First a conventional paper making system will be described.

The drawings illustrate a paper making system that includes a Fourdrinier paper machine. The Fourdrinier machine illustrated normally uses a stock comprising (i) percent of a stock comprising 75 percent virgin groundwood fiber and 25 percent unbleached sulphite stock and (ii) 10 percent broke stock.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings, suitable groundwood stock is prepared and placed in groundwood stock chest 1 1. From here it is pumped through a pipeline 12 to a proportioning and metering box 20.

Sulphite stock is prepared and placed in sulphite stock chest 13. It is pumped from chest 13 through pipeline 14 to the proportioning and metering box 20.

Suitably reconditioned broke stock is stored in broke blend tank 15, from where it is pumped through pipeline 16 to proportioning andmetering box 20. The proportioning and metering box 20 proportions the amount of broke stock, groundwood fibers and sulphite fibers so that a satisfactory mixed stock is passed to mixed stock box 21. The mixed stock goes from box-21 through pipeline 22 to a machine chest 23'. Thus the machine chest 23 has associated with it supply chests for fresh and broke stock a proportioning meter box and a mixed stock box. The mixed stock box may not be present in all paper making systems of the type illustrated in the drawing.

From machine chest 23 the stock is pumped through pipeline 24 to stuflbox 25, which serves as a constant head box to provide the desired amount of fiber to the paper machine. Pipeline 24 feeds the pulp fiber into section 26 of the stufibox 25 where it flows by gravity through section 27 of the stufi'box 25 and down through pipeline 28 to the paper machine circuit. More pulp than required enters section 26 of the stufl'box 25 so that a constant head may be maintained in section 27 of the stuffbox 25. The surplus over-flows out of the stufl'box 25 through pipeline 29 back to the machine chest 23. The pulp from pipeline 28 enters pipeline 30 where it blends with the white water from wirepit 31. It is then pumped by fan pump 32 through pipeline 33 to headbox 34. Headbox 34 distributes the dilute suspension of fibers across a Fourdrinier section 35, where, after suitable pressing and water extraction, it enters the dryer section 36 and is made into a sheet of paper. Excess fiber from the Fourdrinier machine is collected in couchpit 40, which also collects all the stock coming from the headbox 34 when there is a wet end break. This stock collects in couchpit 40 and from couchpit 40 it is pumped through pipeline 41 to a number of locations in the broke handling system depending upon the circumstances. Usually some of the wet broke will be pumped through pipeline 41 to be thickened on a broke filter and then stored in stock chest 42. From stock chest 42 it is pumped through pipeline 43 to the broke storage tank 44.

When there is a wet end break the broke filter is generally too small to handle the complete amount of stock entering the couchpit 40 and some of the broke is pumped through pipeline 41, to pipeline 50, to pipeline 51 and hence directly into the broke storage tank 44. The pumping of excessive broke in this manner can be carried out by the use of valves at the various pipe junctions. As a minor modification of the last mentioned system the wet broke may bypass broke storage tank 44 and be pumped from pipeline 50 to pipeline 52 and, from there, directly to broke blend tank 15.

Any reclaimed, paper fiber, for example the excess trim at the dry end of the paper machine or when there is a dry end break, is recovered in a dry end beater 45. Stock from this beater 45 is suitably treated and pumped through pipeline 46 to the broke storage tank 44.

When broke storage chest 44 is full, rather than sewer the excess .broke it is sometimes pumped through line 54 to groundwood storage chest 11 changing the properties of the groundwood. This of course is undesirable but sometimes necessary.

To supply the proportioning meterbox 20, the broke fiber in the broke storage tank 44 is normally pumped through pipeline 53 to the broke blend tank 15., From here the broke re-enters the paper making process through pipe 16.

The above describes a normal operation of a paper making system. With the large high speed paper machines in use today it must be emphasized that during paper making it is preferable not to interrupt the flow of stock to the paper machine even though the system is not working properly. The preferable practice is not to shut down the paper making system but to rely on the couchpit 40 and the broke system to handle all the stock fed to the machine for example during a break in the paper, as mentioned above.

Throughout the process illustrated diagrammatically in the drawing there would be the normal consistency regulation of the stock, conditioning of the pulp and other practices common to the paper making art. These are not illustrated in the drawing.

In the paper making system of the present invention the problems of excessive broke stock production and the storage of excessive broke stock are overcome by the provision of pipeline 60 and, on certain machines, pipeline 61. When a sheet break or other malfunction occurs on a paper machine in a paper making system according to the present invention the supply of mixed stock from the machine chest is restricted or shut off completely, and a stock is supplied that is completely or mainly broke stock. This has the great advantage of avoiding the creation of new broke during the time that the paper making system is being repaired.

When the sheet breaks on the paper machine of the illustrated system according to the present invention a three-way valve 62 positioned in the pipe 29 before the machine chest 23, diverts the paper stock over-flow through the pipe 61 to the broke blend tank 15. From the broke blend tank 15 stock is pumped by a pump 63 through tank 60 to pipe 24, that is to a point in the paper making system after the machine chest 23. By this means, when any part of the system is malfunctioning, broke stock can bypass 'the machine chest 23 and its associated supply and proportioning means comprising chests 11 and 13, proportioning meter box and mixed stock box 21. The paper machine of the system can thus be kept running on broke stock alone or on substantially broke stock.

The procedure to be followed when the illustrated paper making system of the invention breaks down is: the valve 62 in the pipe 29 is adjusted and the over flow from stuff box is diverted through pipeline 61 to the broke blend tank 15. Simultaneously the pump 63 is started to supply broke stock from the broke blend tank 15 through pipeline 60 to pipe 24 to stuffbox 25. Once sufficient overflow from stufibox 25 has been created the pump that pumps stock from machine chest 23 through pipe 24 in normal operation may be shut down and the paper machine kept going with the fiber from line 60.

When the paper machine has been repaired and it is desired to return to normal operation the pump of the machine chest 23, which contains fresh stock, is started to pump the fresh stock through pipeline 24 to stuffbox 25. Thus fresh stock is delivered to pipeline'28 and to fan pump 32 in a very short time, principally because of the small volume involved. As soon as a suflicient overflow has been created in this way the pump on supply line 60 is shut down and, within a few minutes, line 61 is closed by closing the valve 62. The overflow from stuffbox 25 then goes back to machine chest 23 as previously.

Thus using the present invention it is possible to prevent the waste of good stock and the creation of new broke almost instantaneously by means of pumping operations and valve changes.

It is felt that the use of the pipeline 60 and 61 may not be desirable if the malfunctioning system can be corrected in a few minutes. However for breaks longer than 8-10 minutes the system according to the present invention provides considerable advantages.

Generally speaking the diversion of broke stock to the paper machine of the paper making system of the present invention need not be carried out during the entire sheet break but only during the largest-portion of a long sheet break. Furthermore, it is not suggested here that this invention be limited by circulating only 100 percent of broke stock during the break. There could be times when it would be advantageous to feed, for example, mostly broke stock such as percent broke and 20 percent regular furnish or unused stock.

The stuffbox 25 shown in the drawing is only one type of stock meter that can be used for this purpose in the paper making process. Some stock meters do not require and do not have any overflow section and in these cases in the invention pipeline 29, valve 62, and pipeline 61, would not be required.

It is understood that the flow sheet shown in the drawing is only one of many that could be used to practice the invention. For instance a specific circuit could be to have the pump that pumps stock from the couchpit, pump through an alternative pipeline 65 directly to pipe 24 to supply the stufibox on s sheet break. In this case line 65 could enter into the suction of the machine chest pump that sends stock through pipe 24 to the stufibox 25. Then on a break it could be possible to practice the invention very simply, by starting the big couchpit pump, and when finished, by stopping the big couchpit pump, this being the main control required in this specific circuit.

Further the position of pipe 65 can be varied so that it feeds outflow from the broke filter stock chest 42 to pipe 24. Pipe 65 can also be used to feed stock from couchpit 40 or chest 42 to a point in the paper making system before the suction of the fan pump 32 that feeds stock to the paper machine 35 of the system. Alternatively pipe 65 can be used to supply stock to a point in the system just before the outlet of the head box 34. Using these variations the paper machine of the illustrated system can be kept running on mostly broke stock and relatively very small quantities of fresh stock.

The consistency of the broke stock should be be controlled. It is furthermore suggested that it may be advantageous to control the freeness of the broke stock. This could be accomplished by the addition of specific white-waters to increase of decrease this freeness. Or it could be accomplished by the addition of some other pulp to the broke, or by other means.

The invention described above will give anyone skilled in the art the required information on how he can adapt this invention to his own manufacturing use and to his greatest advantage by the temporary recirculation of a large percentage of broke to the paper machine of a paper making system when the production of good paper has been interrupted.

What] claim as my invention is:

1. In a paper making system that includes 1. a broke tank, couchpit or other receptacle for broke stock fibers and 2. a machine chest or other container that feeds a supply of suitably prepared fibers to the paper machine, the improvement that comprises restricting means for restricting the flow of suitably prepared fibers from the machine chest, feeding means for feeding broke stock fibers from the broke tank, couchpit or other receptacle for broke stock fibers to the paper machine, and means for actuating said feeding means, so that, when the paper making system is malfunctioning, the paper machine can be kept running on substantially broke stock.

2. A system as claimed in claim 1 in which the means for feeding the broke stock fibers is a pipe having associated with it a pump.

3. A system as claimed in claim 2 whereby the pipe feeding broke stock bypasses the machine chest and is connected to a point in the system after the machine chest.

4. A system as claimed in claim 2 whereby the pipe receives its supply of broke stock directly from the couchpit.

system after the machine chest is a point before the outlet of the hcadbox of the paper machine of the system.

8. A system as claimed in claim 1 that includes a stuffbox and means whereby the overflow from the stufibox is made to by-pass the machine chest to a receptacle for broke stock fibers.

I i I II I 

1. In a paper making system that includes
 1. a broke tank, couchpit or other receptacle for broke stock fibers and
 2. a machine chest or other container that feeds a supply of suitably prepared fibers to the paper machine, the improvement that comprises restricting means for restricting the flow of suitably prepared fibers from the machine chest, feeding means for feeding broke stock fibers from the broke tank, couchpit or other receptacle for broke stock fibers to the paper machine, and means for actuating said feeding means, so that, when the paper making system is malfunctioning, the paper machine can be kept running on substantially broke stock.
 2. A system as claimed in claim 1 in which the means for feeding the broke stock fibers is a pipe having associated with it a pump.
 2. a machine chest or other container that feeds a supply of suitably prepared fibers to the paper machine, the improvement that comprises restricting means for restricting the flow of suitably prepared fibers from the machine chest, feeding means for feeding broke stock fibers from the broke tank, couchpit or other receptacle for broke stock fibers to the paper machine, and means for actuating said feeding means, so that, when the paper making system is malfunctioning, the paper machine can be kept running on substantially broke stock.
 3. A system as claimed in claim 2 whereby the pipe feeding broke stock bypasses the machine chest and is connected to a point in the system after the machine chest.
 4. A system as claimed in claim 2 whereby the pipe receives its supply of broke stock directly from the couchpit.
 5. A system as claimed in claim 2 whereby the pipe receives its supply of broke stock from any point in the broke system.
 6. A system as claimed in claim 3 in which the point in the system after the machine chest is a point before the suction of the fan pump that feeds stock to the paper machine of the system.
 7. A system as claimed in claim 3 in which the point in the system after the machine chest is a point before the outlet of the headbox of the paper machine of the system.
 8. A system as claimed in claim 1 that includes a stuffbox and means whereby the overflow from the stuffbox is made to by-pass the machine chest to a receptacle for broke stock fibers. 